The use of fastening devices for the closure of containers, including plastic bag bodies, is generally known. Furthermore, the manufacture of fastening devices made of plastic materials is generally known to those skilled in the art relating to closure devices, as demonstrated by the numerous patents in this area.
A particularly well-known use for fastening devices is in connection with flexible containers, such as bag bodies. The closure device and the associated container may be formed from thermoplastic materials, and the closure device and sidewalls of the container can be integrally formed by extrusion as a single piece. Alternatively, the closure device and sidewalls may be formed as separate pieces and then connected by heat sealing or any other suitable connecting process. The closure devices, when incorporated as fasteners on bag bodies, have been particularly useful in providing a closure means for retaining the contents of the bag body within the bag body.
Conventional closure devices utilize mating male and female closure elements which are occluded to effect closure of the device. It is often difficult to determine when the male and female closure elements are occluded. Accordingly, when conventional closure devices are employed, there exists a likelihood that the closure device is at least partially open.
The prior art discloses closure devices that attempt to resolve these issues. For example, the prior art has provided various closure devices having male and female closure elements, wherein one of the closure elements is blue and the other is yellow. When the blue and yellow closure elements are properly occluded, the closure device appears green, thus providing a visual confirmation that the closure device has been properly occluded. The change in color that is viewed when dissimilarly colored male and female members are occluded is demonstrated in a commercially available product sold under the trademark GLAD-LOCK® (Glad-Lock is the registered trademark of The Glad Products Company, Oakland, Calif.).
The aforementioned GLAD-LOCK® product has provided a closure device that overcomes the drawbacks inherent in previously known devices, and has enjoyed considerable consumer acceptance. Notwithstanding the commercial acceptance of the aforementioned product, improved closure devices are continually sought. It has been observed that the color-changing property of a closure device is most effective when the width of the closure element is relatively narrow, that is, when the closure device has a width of about 90 mils. However, when the closure device is narrow, it is more difficult to properly align the closure elements of such a closure device. Accordingly, it has been found that consumers prefer closure devices having a width on the order of about 180 mils to about 380 mils.
When the width of the closure device is increased, however, the effectiveness of the color-changing indicator can be somewhat diminished. The color change effect between occluded and unoccluded is diminished. In the aforementioned GLAD-LOCK® product, the color-changing effect is accomplished by forming one of the closure elements as an opaque yellow color and the other as a translucent blue color. The green color obtained upon occlusion of the two closure elements is viewed through the translucent blue-colored element. As the closure elements are made larger to accommodate consumer preferences, there is more area to provide for visual overlap between the opaque yellow and translucent blue closure elements when the closure elements are not fully occluded. The color of the blue element thus may appear to be blue-green at the points or regions where the elements are in close proximity but are unoccluded. Therefore, the contrast between the appearance of the translucent blue closure element in the unoccluded state and the occluded state is reduced.
A need accordingly exists for a wider closure device that more easily may be occluded by a user while also effectively exhibiting the visual color-changing effect provided by narrower closure devices. The prior art has disclosed several solutions to the aforesaid use of wider closure devices, including, for example, a closure device that incorporates a color-changing enhancement member within the device to improve the color change perception in wider color change closure devices. One such improved color change closure device is disclosed in U.S. Pat. No. 4,829,641. Although this color-change closure device enhanced color-changing effectiveness in wider closure devices and is beneficial, a further improvement in a color-changing closure device is beneficial as the closure device gets wider. A need therefore exists for a color change closure device capable of high contrast between the different colors viewable in the occluded and unoccluded states and has the desired width for tactile manipulation.
It is a general object of the present invention to provide a closure device that satisfies the foregoing needs.